Toro 4500 deck creep

All, we have a 8 year old Toro 4500 with about 1500 hours. The front outside decks are dropping after they are raised. It is a fast creep and there is significant drop after about 10 seconds.
Both of the cylinders from those arms have been rebuilt and tested by a qualified shop.
Is there something we are missing to keep the decks up when raised?